Is the negative cashflow after management, repairs, capex, vacancy etc. ? 

If the property is leased you go off the lease agreement X .75% of the lease amount (to account for property management / Cap X / Maintenance / Vacancy) minus the mortgage.

My goal is to have 20k to invest and to be safe I want an extra 5k to have a backup in case of unplanned costs due to inexperience in the buying process, having vacancy the first months, etc...Question 1: Does it make sense to minimize my 401k contribution to nearly nothing to speed up my savings for REI?

.$10k closing costs looks very high to me.I use 8% Vacancy when underwriting MFR.Insurance looks very low for a $650k property.

You should be able to get a 4-5 cap duplex (a true cap rate, after accounting for vacancy, leasing, management, R&M, etc) with decent appreciation potential.Good luck and welcome to BP!

I send monthly emails with property updates, which include vacancies, number of units that we’ve renovated, operating income reports, and more.

I have many exclusive listings, in 17 years, I have never had a vacancy .

Nothing yet, upon vacancy I plan on rehabbing bathroom and carpeting.

I am stabilizing my newly purchase properties atm and have elected to do it one at a time to increase the rent roll because they're so terribly low but am keeping my other buildings as is to minimize vacancy and stress level. 

- In past oil crises, have you seen significant vacancies?